Increasingly, a plurality of electronic appliances are being interconnected using a network, even in the field of home electronics, so that electronic data can be interchanged between the appliances. The electronic data interchange between the electronic appliances then takes place within the network not just via cable connections between the appliances, for example on the basis of IEEE1394 bus systems, but also using wireless connections. There are already various systems which can be used for wirelessly transmitting electronic data between such appliances. In this context, the system “Hiperlan2” may be cited, in particular. The Hiperlan2 system allows appliances to be connected together in a network, for example home electronics appliances.
A basic requirement when operating the network with a plurality of appliances between which electronic data are interchanged is that the electronic data be transmitted between one or more of the connected appliances with as little error as possible. If errors arise when transmitting the data, they need to be recognized and possibly corrected. For this purpose, systems such as “Hiperlan2” provide a mode of operation in which, during data transmission between a transmitter apparatus and a receiver apparatus which are connected to the network together, the detection of an incorrect data packet in the receiver apparatus automatically generates a request for a repeat transmission of the incorrect data packet (ARQ—“Automatic Repeat request”) and sends it to the transmitter apparatus. In this way, the transmitter apparatus is informed, in particular, about an error status for each received-data packet received incorrectly in the receiver apparatus. The receiver apparatus generates a feedback message which indicates whether or not a received-data packet received in the receiver apparatus contains an error. The presence or absence of an error is indicated using associated error status data for each received-data packet in the receiver apparatus. The check to determine whether or not there is an error is carried out in the receiver apparatus using an error recognition code (for example CRC—“Cyclic Redundancy Check”) which the data packets received by the receiver apparatus contain.
The receiver apparatus has a receiver memory with a receiver memory area which is used to store the received-data packets and the respective associated error status data. The receiver memory area with the received-data packets and the error status data corresponds to a transmitter memory area in a transmitter memory in the transmitter apparatus from which transmission-data packets have been transmitted to the receiver apparatus. To ensure functional operation of the electronic data interchange between the transmitter apparatus and the receiver apparatus, it is necessary for the transmitter memory area and the receiver memory area to be synchronized. This is done using the feedback message described.
When it is being processed in the transmitter apparatus, the feedback message can first of all be used to provide information about the error status of the received-data packets in the receiver memory area, so that the transmitter apparatus can subsequently update the information about the data packets in the transmitter memory area by assigning the transmission-data packets in the transmitter memory area a respective status which corresponds to the status of the associated received-data packet in the receiver memory area.
In order to carry out the synchronization between the receiver memory area and the transmitter memory area correctly, it is also necessary for the feedback message to include an explicit reference identification which ensures correct association of the information from the feedback message between received-data packets in the receiver memory area and transmission-data packets in the transmitter memory area. The reference identification identifies a received-data packet which is used to stipulate the location of the receiver memory area in the receiver memory, for example the first received-data packet in the receiver memory area. Since the reference identification can be used to assign the received-data packet an associated transmission-data packet in the transmitter memory area, this allows the transmitter memory area and the receiver memory area to be stipulated, so that the two memory areas include data packets which can be associated with one another.
In this context, provision can be made for the reference identification to be a bitmap block number (BMN). The bitmap block numbers are derived for single received/transmission-data packets from a sequence number explicitly associated with the respective data packet. However, this procedure has the problem that the reference identification for the feedback message is sometimes derived on the basis of the sequence number of a received-data packet which has itself been transmitted incorrectly between the transmitter apparatus and the receiver apparatus, which prevents correct synchronization of the transmitter memory area and the receiver memory area.